Refinement of triclinic lysozyme: I. Fourier and least-squares methods.
X-ray diffraction data to 1.5 A resolution have been collected for triclinic crystals of hen egg white lysozyme. The triclinic model was derived from the tetragonal one by the rotation function and refined initially by Fo-Fc and differential difference syntheses against 2 A resolution data. Refinement was continued by differential difference cycles against the 1.5 A data until R was reduced to 0.220. Although the initial refinement was rapid, it was subsequently a matter of attrition, leading to a complete recheck of the data and the discovery of systematic error which affected primarily the high-resolution data. Refinement was continued against the corrected 2 A data by block-diagonal least squares. After five cycles the refinement was terminated at R = 0.254 because of the imminent availability of a preferred refinement program. Problems with the protein model, the solvent, and the interaction of the scale and thermal parameters are discussed. The experiences gained in this study are summarized.
Hodsdon
J M
JM
Department of Biological Structure, University of Washington, Seattle 98195.
Brown
G M
GM
Sieker
L C
LC
Jensen
L H
LH
D005583:Fourier Analysis; D016018:Least-Squares Analysis; D008956:Models, Chemical; D009113:Muramidase; D014961:X-Ray Diffraction
D009113:Muramidase